Modulation of the Development of Humoral Immunity by Topically Applied Acetone, Ethanol, and 12-O-Tetradecanoylphorbol-13-Acetate

The effects of topically applied 12-O-tetradecanoylphorbol-13-acetate (TPA), acetone, and ethanol on systemic immune function were analyzed in SSIN mice. A total of one, four, or eight dorsal applications of solvent (50-300 microl/treatment, 2x/week) affected neither the overall cellularity of the spleen nor the relative proportions of splenic cells expressing CD4, CD8, or Ig surface markers. In contrast, overall cellularities of the spleen increased and relative T cell content of the spleen decreased in mice treated multiple times with TPA (2 microg/application in 0.2 ml acetone). The development of splenic B cells secreting IgM against sheep red blood cells (SRBC, a T-cell-dependent antigen) was retarded, and the overall duration of IgM synthesis was decreased, in mice immunized 1 hr after the last of four applications (>200 microl) of either solvent. Comparable retardations occurred in mice immunized as late as 7 days after termination of solvent treatment. However, solvent effects on the development of antibody-forming cells were not observed after eight topical applications or when TNP-LPS (a T-cell-independent antigen) was used as the immunogen. The effects of TPA on the development of IgM-secreting B cells were indistinguishable from those of the solvent used for its application. Although serum hemagglutination titers to SRBC correlated with the relative numbers of splenic B cells producing IgM, in vitro proliferative responses to B and T cell mitogens were not predictive of the effects of solvents or TPA on the development of antibody-secreting cells. Collectively, these studies demonstrate that topically applied acetone and ethanol can systemically modulate humoral immunity and emphasize the need for inclusion of nontreated controls when assessing the potential immunomodulatory activities of agents dissolved in acetone or ethanol.